There are many circumstances in human and animal medicine where it is necessary to keep a patient warm to, for example, prevent or treat hypothermia. Forced warm air heating systems have been designed to keep patients warm during surgery and during critical care (e.g. recovery post-surgery).
Forced warm air heating systems were originally designed for use in human medicine only, for the prevention and treatment of hypothermia during anaesthesia and in critical care. Primarily, the blankets were placed over patients recovering from anaesthesia. Recently blankets have been designed to provide warm air heating for animals during surgery and recovery (see the applicant's earlier International Patent Application No. PCT/AU2003/001626, the disclosure of which is incorporated herein by reference).
Forced warm air heating systems usually comprise a blanket-type arrangement which comprises at least two layers forming a hollow space between them when air is delivered to the space. The blanket or a portion of the blanket may include one or more air holes or it may be of a porous/permeable material, to allow warmed air through the blanket to warm the patient. For small animals, blankets of or having a portion of permeable/porous material are preferred so that the warm air is diffused over the surface of the material (for example, the design disclosed in applicant's earlier PCT application No. PCT/AU2003/001626).
Forced warm air heating systems also include a heating unit for providing the warmed air, and a conduit, which may be in the form of a hose and/or pipe for delivering the warmed air from the heating unit to the blanket arrangement.
Animal patients during critical care or recovery (e.g. post anaesthesia) are usually caged for their restraint and safety (semi-conscious animals move about and can become injured through misadventures such as falling off treatment tables). Where an animal needs to be warmed during care, in the cage, this leads to a problem in using warmed air heating systems. The heater (with an electricity supply and heating unit, etc) must be placed outside the cage and any blanket arrangement must obviously be placed in the cage. There is therefore difficulty in providing the warm air conduit from the heater to the patient through the cage. The cage door must be properly shut so that the animal can't fall out. This problem is exacerbated by the fact that there are many different types of cages provided for veterinary patients, which, for example, have different diameters of bars, different grill patterns or grill widths for the cage and cage doors. These problems prevent currently available hoses/piping providing heating conduits from being able to pass through a cage or cage door into a cage.
Presently available warm air blanket arrangements typically have only one port by which warm air can enter the blanket (via the conduit). Generally, it is not convenient for the blanket to be moved once the patient is in the cage. Having only one port, say at the head of the blanket, may make it difficult for the warm air to be provided to the blanket without moving it. Having the port at the head end of the blanket (which is usually the case) in many cases, does not provide a convenient position for introducing the warmed air conduit to the port when the blanket arrangement is positioned within a cage.
Cages for animals in veterinary establishments are usually of a form having a solid bottom, ceiling and sides (which may be of metal or wood) and then one or two barred doors on the front of the cage, which swing fully open. As discussed above, trying to pass warmed air from a forced warmed air heating system via a conduit into the cage is difficult. The only option may be the cage door, which presents the further difficulty that the cage door must be able to be opened, sometimes quickly for urgent access.